GPR, or ground-penetrating RADAR (where RADAR is “RAdio Detection And Ranging), is a technology used to assess the composition and location of heterogeneous materials. GPR uses radio frequencies and is particularly useful in that it is both non-destructive and non-ionizing. In fact, GPR uses frequencies similar to a cellular phone, but at far lower power levels. Common applications include locating the precise position of rebar within a concrete wall/floor, identifying and locating buried objects underground, assessing the quality and uniformity of an asphalt or concrete highway surface, and detecting deterioration on bridge decks. In road surface applications, GPR is used, for example, to detect cracks, fissures, or contamination in any one of the chip seal, pavement layers, gravel base, and so forth. In many roadway applications, a resolution of features of the road surface of less than one inch (2.54 cm) is desired. Such systems may be mounted on vehicles, travelling over the surface while acquiring measurement data. GPR systems are disclosed in more detail in U.S. Pat. No. 5,499,029 to Bashforth, et al., and U.S. Pat. No. 5,384,715 to Lytton, which are hereby incorporated by reference.
Ground Penetrating Radar (GPR) antennas are built in different sizes for different uses. Smaller antennas are generally higher in frequency, have higher resolution for displaying finer details and are not able to penetrate as deep as lower frequency antennas. Larger antennas are generally lower in frequency, are able to penetrate deeper, but have a lower resolution, and so are not able to discriminate fine details. By performing a survey simultaneously with two antennas, a higher and a lower frequency model, the user is able to obtain the best of each antenna. The volume near the surface will have the best resolution, and the deeper volume will be viewed with the maximum range. Viewing the two separate pictures displayed can be difficult for the average user, even when viewed on the same monitor, as is the best practice currently known.
Therefore, when employing ground penetrating radar there is a need in the art to find a better way to present the shallow, fine details of high resolution with the deeper penetration information of low resolution.